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변형구배 결정소성 유한요소해석법을 이용한 니켈기 다결정 합금의 Hall-Petch 관계 모델링
최윤석,조경목,남대근,최일동,Choi, Yoon Suk,Cho, Kyung-Mox,Nam, Dae-Geun,Choi, Il-Dong 한국재료학회 2015 한국재료학회지 Vol.25 No.2
A strain-gradient crystal plasticity constitutive model was developed in order to predict the Hall-Petch behavior of a Ni-base polycrystalline superalloy. The constitutive model involves statistically stored dislocation and geometrically necessary dislocation densities, which were incorporated into the Bailey-Hirsch type flow stress equation with six strength interaction coefficients. A strain-gradient term (called slip-system lattice incompatibility) developed by Acharya was used to calculate the geometrically necessary dislocation density. The description of Kocks-Argon-Ashby type thermally activated strain rate was also used to represent the shear rate of an individual slip system. The constitutive model was implemented in a user material subroutine for crystal plasticity finite element method simulations. The grain size dependence of the flow stress (viz., the Hall-Petch behavior) was predicted for a Ni-base polycrystalline superalloy NIMONIC PE16. Simulation results showed that the present constitutive model fairly reasonably predicts 0.2%-offset yield stresses in a limited range of the grain size.
Glucose Transporter-1 Expression in Squamous Cell Carcinoma of the Tongue
최윤석,Seok Jin Kim,Dae Sik Kim,Seh Jong Park,Yong Park,Hye Jin Shin,Kwang-Yoon Jung,Seung-Kuk Baek,Bong Kyung Shin,Jung Woo Choi,Byung Soo Kim,Sang Won Shin,Yeul Hong Kim,Jun Suk Kim 대한암학회 2007 Cancer Research and Treatment Vol.39 No.3
Purpose: Tumor cells are known to express hypoxia-related proteins such as glucose transporter-1 (Glut-1). These hypoxia-induced changes may allow tumor cells to survive under sustained hypoxic microenvironments, and the surviving tumor cell under hypoxia may develop a more aggressive phenotype and so result in a poor prognosis. Materials and Methods: The Glut-1 expression was analyzed by immunohistochemistry, and its association with the prognosis was assessed in 60 patients with squamous cell carcinoma of the tongue.Results: The Glut-1 expression was diffuse with a membranous pattern, and the median percentage of Glut-1 positive tumor cells was 60% (range: 0.0∼90.0%). A high Glut-1 expression (the percentage of positive tumor cells ≥ the median value, 60%) was associated with the location of primary lesion, lymph node metastasis status and disease stage (p〈0.05).Theexpression of Glut-1 was correlated with the Ki-67 expression (r=0.406, p=0.001). Microvessel density, as represented by CD31 staining, was also correlated with the Glut-1 expression although its significance is weak (r=0.267, p=0.039). On the univariate analysis, the group with a high Glut-1 expression showed poorer overall survival than the group with a low Glut-1 expression (p〈0.05). However, the Glut-1 expression failed to show any independent prognostic significance on the multivariate analysis.Conclusion: The expression of Glut-1 may be useful for predicting the prognosis and determining the treatment strategy for the management of squamous cell carcinoma of the tongue. (Cancer Res Treat. 2007;39:109-115)
산업폐자원을 포함한 모르타르 시험체의 저에너지 차폐 특성
최윤석 ( Choi Yoon Suk ),강동원 ( Gang Dong Won ),김일순 ( Kim Il Sun ),최소영 ( Choi So Yeong ),양은익 ( Yang Eun Ik ) 한국구조물진단유지관리공학회 2018 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.22 No.1
Environmental pollution is the major problem associated with rapid industrialization, urbanization and rise in living standards of people. In order to reduce environmental pollution, therefore, shielding materials using industrial waste resources were developed and the radiation shielding performance was evaluated.